Method for manufacturing a spin valve having an enhanced free layer

ABSTRACT

A spin valve sensor is provided with a negative ferromagnetic coupling field −H FC  for properly biasing a free layer and a spin filter layer is employed between the free layer and a capping layer for increasing the magnetoresistive coefficient dr/R of the spin valve sensor. A top portion of the free layer is oxidized for improving the negative ferromagnetic coupling field −H FC  when the spin filter layer is employed for increasing the magnetoresistive coefficient dr/R.

REFERENCE TO RELATED APPLICATION

This is a divisional of application Ser. No. 09/753,968 filed Jan. 2,2001, now U.S. Pat. No. 6,700,757.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an enhanced free layer for a spin valvesensor and, more particularly, to such a free layer and a method ofmaking wherein a desirable negative ferromagnetic coupling field ismaintained when a copper layer is located between the free layer and acapping layer for the purpose of increasing a magnetoresistivecoefficient dr/R of the spin valve sensor.

2. Description of the Related Art

The heart of a computer is a magnetic disk drive which includes arotating magnetic disk, a slider that has read and write heads, asuspension arm above the rotating disk and an actuator arm that swingsthe suspension arm to place the read and write heads over selectedcircular tracks on the rotating disk. The suspension arm biases theslider into contact with the surface of the disk when the disk is notrotating but, when the disk rotates, air is swirled by the rotating diskadjacent an air bearing surface (ABS) of the slider causing the sliderto ride on an air bearing a slight distance from the surface of therotating disk. When the slider rides on the air bearing the write andread heads are employed for writing magnetic impressions to and readingmagnetic field signals from the rotating disk. The read and write headsare connected to processing circuitry that operates according to acomputer program to implement the writing and reading functions.

An exemplary high performance read head employs a spin valve sensor forsensing the magnetic field signals from the rotating magnetic disk. Thesensor includes a nonmagnetic electrically conductive spacer layersandwiched between a ferromagnetic pinned layer and a ferromagnetic freelayer. An antiferromagnetic pinning layer interfaces the pinned layerfor pinning the magnetic moment of the pinned layer 90° to the airbearing surface (ABS). First and second leads are connected to the spinvalve sensor for conducting a sense current therethrough. A magneticmoment of the free layer is free to rotate upwardly and downwardly withrespect to the ABS from a quiescent or zero bias point position inresponse to positive and negative magnetic signal fields from therotating magnetic disk. The quiescent position of the magnetic moment ofthe free layer, which is preferably parallel to the ABS, is when thesense current is conducted through the sensor without magnetic fieldsignals from the rotating magnetic disk. If the quiescent position ofthe magnetic moment is not parallel to the ABS the positive and negativeresponses of the free layer will not be equal which results in readsignal asymmetry, which is discussed in more detail hereinbelow.

The sensitivity of the spin valve sensor is quantified asmagnetoresistive coefficient dr/R where dr is the change in resistanceof the spin valve sensor from minimum resistance (magnetic moments offree and pinned layers parallel) to maximum resistance (magnetic momentsof the free and pinned layers antiparallel) and R is the resistance ofthe spin valve sensor at minimum resistance. Because of the highmagnetoresistance of a spin valve sensor it is sometimes referred to asa giant magnetoresistive (GMR) sensor. Changes in resistance of the spinvalve sensor are a function of cos θ, where θ is the angle between themagnetic moments of the pinned and free layers. When a sense current isconducted through the spin valve sensor, resistance changes causepotential changes that are detected and processed as playback signalsfrom the rotating magnetic disk.

The transfer curve for a spin valve sensor is defined by theaforementioned cos θ where θ is the angle between the directions of themagnetic moments of the free and pinned layers. The bias point should belocated midway between the top and bottom of the transfer curve. Whenthe bias point is located below the midway point the spin valve sensoris negatively biased and has positive asymmetry and when the bias pointis above the midway point the spin valve sensor is positively biased andhas negative asymmetry. The location of the transfer curve relative tothe bias point is influenced by four major forces on the free layer of aspin valve sensor, namely a ferromagnetic coupling field H_(FC) betweenthe pinned layer and the free layer, a net demagnetizing (demag) fieldHD from the pinned layer, a sense current field H_(I) from allconductive layers of the spin valve except the free layer, a net imagecurrent field H_(IM) from the first and second shield layers. Thestrongest magnetic force on the free layer structure is the sensecurrent field H_(I).

SUMMARY OF THE INVENTION

In the present invention a negative ferromagnetic coupling field −H_(FC)is obtained for the purpose of counterbalancing other magnetic fieldsacting on the free layer so as to more adequately position the biaspoint on the transfer curve of the spin valve sensor. In a preferredembodiment this is accomplished by providing a pinning layer which iscomposed of platinum manganese (PtMn) and providing a first seed layercomposed of nickel manganese oxide (NiMnO) and a second seed layercomposed of tantalum (Ta) wherein the first seed layer interfaces thefirst read gap layer, which is composed of aluminum oxide (Al₂O₃), andthe second seed layer is located between the first seed layer and thepinning layer. The invention further includes a copper (Cu) layer whichis located between the free layer and a capping layer wherein thecapping layer is preferably tantalum (Ta). The purpose of the copper(Cu) layer, which is also referred to as a spin filter layer, is toincrease the magnetoresistive coefficient dr/R. Unfortunately, the spinfilter layer reduces the magnitude of the negative ferromagneticcoupling field which is being sought for proper balancing of the freelayer. Further, the spin filter layer can result in a decrease of themagnetoresistive coefficient dr/R instead of an increase.

The present invention obviates reduction of the negative ferromagneticcoupling field by oxidizing a top of the free layer before formation ofthe capping layer. This may be accomplished by first sputter depositingthe top of the free layer, which may be nickel iron (NiFe) or cobaltiron (CoFe) or cobalt (Co), and then introducing oxygen into asputtering chamber for oxidizing the top of the deposited layer.Accordingly, the free layer has an oxidized film portion and anunoxidized film portion wherein the oxidized film portion is locatedbetween the unoxidized film portion and the capping layer. In myexperiments I have shown that without the spin filter layer the negativeferromagnetic coupling field −H_(FC) is about −16 Oe, that when the spinfilter layer is added the negative ferromagnetic coupling field −H_(FC)is degraded to about −8 Oe, and that when the top of a nickel iron(NiFe) free layer is oxidized before forming the capping layer that thenegative ferromagnetic coupling field −H_(FC) is restored to −16 Oe.Further studies optimized the magnetoresistive coefficient dr/R of thepresent invention by appropriately sizing the thickness of the copperlayer. The magnetoresistive coefficient dr/R was maximized when thethickness of the copper layer was about 6 Å. The invention also includesoxidizing fully or a top portion of the copper layer and/or oxidizingtop portions of multiple films of the free layer and capping layers.

Another aspect of the invention is that when the copper spacer layer ofthe spin valve sensor is made thinner the dr/R is increased. However,when the thickness of the spacer layer is decreased the ferromagneticcoupling field increases which may adversely affect the biasing of thefree layer. The present invention enables the spin filter layer to beemployed for increasing the dr/R in combination with a thinner spacerlayer for further increasing the dr/R. When a negative ferromagneticcoupling field −H_(FC) of −16 Oe is obtained by the present inventionthe more positive ferromagnetic coupling field due to a thinner spacerlayer is offset by the −16 Oe. A resultant −8 Oe or lower can still beused effectively for properly biasing the free layer.

An object of the present invention is to provide a spin valve sensorwherein a negative ferromagnetic coupling field H_(FC) is not degradedwhen a copper layer is employed between a free layer and a capping layerfor the purpose of increasing the magnetoresistive coefficient dr/R ofthe spin valve sensor.

Another object is to accomplish the foregoing object as well asappropriately sizing the copper layer so as to optimize themagnetoresistive coefficient dr/R.

Other objects and attendant advantages of the invention will beappreciated upon reading the following description taken together withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2 of FIG. 1;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the magnetic head taken along plane 5—5 of FIG.2;

FIG. 6 is a partial view of the slider and a piggyback magnetic head asseen in plane 6—6 of FIG. 2;

FIG. 7 is a partial view of the slider and a merged magnetic head asseen in plane 7—7 of FIG. 2;

FIG. 8 is a partial ABS view of the slider taken along plane 8—8 of FIG.6 to show the read and write elements of the piggyback magnetic head;

FIG. 9 is a partial ABS view of the slider taken along plane 9—9 of FIG.7 to show the read and write elements of the merged magnetic head;

FIG. 10 is a view taken along plane 10—10 of FIG. 6 or 7 with allmaterial above the coil layer and leads removed;

FIG. 11 is an enlarged isometric illustration of a read head which has aspin valve sensor;

FIG. 12 is an ABS illustration of a spin valve sensor wherein a negativeferromagnetic coupling field −H_(FC) is obtained;

FIG. 13 is the same as FIG. 12 except a copper layer is located betweenthe free layer and a capping layer;

FIG. 14 is the same as FIG. 13 except a top portion of the free layerhas been oxidized;

FIG. 15 is the same as FIG. 14 except a top portion of the copper layeris also oxidized;

FIG. 16 is the same as FIG. 15 except the copper spacer layer is 6 Åthick instead of 10 Å thick;

FIG. 17 is a chart showing the change in a negative ferromagneticcoupling field −H_(FC) in various Examples 1-4;

FIG. 18 is a chart showing the change in resistance R of the spin valvesensor with various thicknesses of a copper layer in Example 3;

FIG. 19 is a chart showing the change in resistance dr of the spin valvesensor with various thicknesses of the copper layer in Example 3;

FIG. 20 is a chart showing the change in a magnetoresistive coefficientdr/R of the spin valve sensor with various thicknesses of the copperlayer in Example 3;

FIG. 21 is a chart showing the change in uniaxial anisotropy fieldH_(K with) various thicknesses of the copper layer in Example 3;

FIG. 22 is a change in easy axis coercivity H_(C) of a spin valve sensorwith various thicknesses of the copper layer in Example 3;

FIG. 23 is an ABS illustration of another embodiment of the inventionwherein the free layer has a top film composed of cobalt iron (CoFe)which has a top oxidized portion;

FIG. 24 is the same as FIG. 23 except additional films composed ofnickel iron (NiFe) and cobalt iron (CoFe) of the free layer haveoxidized portions; and

FIG. 25 is the same as FIG. 24 except the copper layer has a topoxidized portion.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, FIGS. 1-3 illustratea magnetic disk drive 30. The drive 30 includes a spindle 32 thatsupports and rotates a magnetic disk 34. The spindle 32 is rotated by aspindle motor 36 that is controlled by a motor controller 38. A slider42 has a combined read and write magnetic head 40 and is supported by asuspension 44 and actuator arm 46 that is rotatably positioned by anactuator 47. A plurality of disks, sliders and suspensions may beemployed in a large capacity direct access storage device (DASD) asshown in FIG. 3. The suspension 44 and actuator arm 46 are moved by theactuator 47 to position the slider 42 so that the magnetic head 40 is ina transducing relationship with a surface of the magnetic disk 34. Whenthe disk 34 is rotated by the spindle motor 36 the slider is supportedon a thin (typically, 0.05 μm) cushion of air (air bearing) between thesurface of the disk 34 and the air bearing surface (ABS) 48. Themagnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 34, as well as forreading information therefrom. Processing circuitry 50 exchangessignals, representing such information, with the head 40, providesspindle motor drive signals for rotating the magnetic disk 34, andprovides control signals to the actuator for moving the slider tovarious tracks. In FIG. 4 the slider 42 is shown mounted to a suspension44. The components described hereinabove may be mounted on a frame 54 ofa housing, as shown in FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

FIG. 6 is a side cross-sectional elevation view of a piggyback magnetichead 40, which includes a write head portion 70 and a read head portion72, the read head portion employing a dual spin valve sensor 74 of thepresent invention. FIG. 8 is an ABS view of FIG. 6. The spin valvesensor 74 is sandwiched between nonmagnetic electrically insulativefirst and second read gap layers 76 and 78, and the read gap layers aresandwiched between ferromagnetic first and second shield layers 80 and82. In response to external magnetic fields, the resistance of the spinvalve sensor 74 changes. A sense current I_(S) conducted through thesensor causes these resistance changes to be manifested as potentialchanges. These potential changes are then processed as readback signalsby the processing circuitry 50 shown in FIG. 3.

The write head portion 70 of the magnetic head 40 includes a coil layer84 sandwiched between first and second insulation layers 86 and 88. Athird insulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. An insulation layer 103 is locatedbetween the second shield layer 82 and the first pole piece layer 92.Since the second shield layer 82 and the first pole piece layer 92 areseparate layers this head is known as a piggyback head. As shown inFIGS. 2 and 4, first and second solder connections 104 and 106 connectleads from the spin valve sensor 74 to leads 112 and 114 on thesuspension 44, and third and fourth solder connections 116 and 118connect leads 120 and 122 from the coil 84 (see FIG. 10) to leads 124and 126 on the suspension.

FIGS. 7 and 9 are the same as FIGS. 6 and 8 except the second shieldlayer 82 and the first pole piece layer 92 are a common layer. This typeof head is known as a merged magnetic head. The insulation layer 103 ofthe piggyback head in FIGS. 6 and 8 is omitted.

FIG. 11 is an isometric ABS illustration of the read head 72 shown inFIG. 6 or 8. The read head 72 includes the present dual spin valvesensor 74 which is located on an antiferromagnetic (AFM) pinning layer132. First and second hard bias and lead layers 134 and 136 areconnected to first and second side edges 138 and 140 of the spin valvesensor. This connection is known in the art as a contiguous junction andis fully described in commonly assigned U.S. Pat. No. 5,018,037 which isincorporated by reference herein. The first hard bias and lead layers134 include a first hard bias layer 140 and a first lead layer 142 andthe second hard bias and lead layers 136 include a second hard biaslayer 144 and a second lead layer 146. The hard bias layers 140 and 144cause magnetic fields to extend longitudinally through the spin valvesensor 130 for stabilizing the magnetic domains therein. The spin valvesensor 130 and the first and second hard bias and lead layers 134 and136 are located between nonmagnetic electrically insulative first andsecond read gap layers 148 and 150. The first and second read gap layers148 and 150 are, in turn, located between ferromagnetic first and secondshield layers 152 and 154.

EXAMPLE 1

FIG. 12 shows a spin valve sensor 200 which is located on the first readgap (G1) 148 wherein the first read gap is composed of aluminum oxide(Al₂O₃). The spin valve sensor 200 includes a pinned layer 202 which hasa magnetic moment 204 which is pinned by an antiferromagnetic (AFM)pinning layer 206. The magnetic moment 204 is pinned perpendicular tothe ABS in a direction toward the ABS or away from the ABS, as shown inFIG. 12. In this example the pinned layer was an antiparallel (AP)pinned layer which included an antiparallel coupling layer (APC) 208which was located between ferromagnetic first and second antiparallellayers (AP1) and (AP2) 210 and 212. A spacer layer (S) 214 is locatedbetween the second AP pinned layer 212 and a free layer 216 which has amagnetic moment 218 which is oriented parallel to the ABS and parallelto the major thin film surfaces of the layers when the bias point of thespin valve sensor is located midway on its transfer curve. The freelayer 216 includes first and second free films (F1) and (F2) 220 and222. On top of the second free film 222 is a cap layer 224. First andsecond seed layers (SL1) and (SL2) 226 and 228 are provided between thefirst read gap layer 148 and the pinning layer 206 with the second seedlayer 228 being located between the first seed layer 226 and the pinninglayer 206.

Exemplary thicknesses of the Al₂O₃ first read gap layer 146 are 200Å-700Å. The thicknesses and materials of the other layers are 30 Å of nickelmanganese oxide (NiMnO) for the first seed layer 226, 35 Å of tantalum(Ta) for the second seed layer 228, 175 Å of platinum manganese (PtMn)for the pinning layer 206, 17 Å of cobalt iron (CoFe) for the first APpinned layer 210, 8 Å of ruthenium (Ru) for the antiparallel couplinglayer 208, 26 Å of cobalt iron (CoFe) for the second AP pinned layer212, 20 Å of copper (Cu) for the spacer layer 214, 15 Å of cobalt iron(CoFe) for the first free film 220, 25 Å of nickel iron (NiFe) for thesecond free film 222 and 50 Å of tantalum (Ta) for the cap layer 224.

A sense current I_(S) may be directed from right to left or from left toright as shown in FIG. 12. When a field signal from a rotating magneticdisk rotates the magnetic moment 218 upwardly into the sensor themagnetic moments 204 and 218 become more parallel which reduces theresistance of the sensor to the sense current I_(S) and when a fieldsignal from the rotating magnetic disk rotates the magnetic moment 218downwardly out of the sensor the magnetic moments 204 and 218 becomemore antiparallel which increases the resistance of the sensor to thesense current I_(S). These increases and decreases in the resistance ofthe spin valve sensor are processed as playback signals by theprocessing circuitry 50 in FIG. 3.

As discussed in the Summary of the Invention various magnetic forcesaffect the positioning of the magnetic moment 218 of the free layer. Thefree layer is properly biased by these magnetic forces when the magneticmoment 218 is parallel to the ABS, as shown in FIG. 12. A negativeferromagnetic coupling field −H_(FC) is desirable for counterbalancingone or more of these magnetic forces for properly biasing the free layer216. This negative ferromagnetic coupling field has been achieved byemploying the pinning layer 206 composed of platinum manganese (PtMn)and the first and second seed layers 226 and 228 which are composed ofnickel manganese oxide (NiMnO) and tantalum (Ta) respectively. Further,the first seed layer 226 must interface an aluminum oxide (Al₂O₃) firstread gap layer 148 or be located on an aluminum oxide (Al₂O₃) seed layerwhich is approximately 30 Å thick. The spin valve sensor 200 in FIG. 12was tested for its ferromagnetic coupling field −H_(FC) and it was foundto be −16 Oe, which is shown at Example 1 in FIG. 17.

It should be noted that when the spacer layer 214 is decreased inthickness that the magnetoresistive coefficient dr/R is increased.However, when the spacer layer 214 is decreased in thickness theferromagnetic coupling field −H_(FC) increases in a positive direction,which may adversely affect biasing of the free layer 216. Accordingly,the negative ferromagnetic coupling field −H_(FC) of −16 Oe in Example 1is desirable because the thickness of the spacer layer 214 can now bereduced to increase the dr/R and the increase in the ferromagneticcoupling field due to the thinner spacer layer can be offset by a partof the −16 Oe.

EXAMPLE 2

FIG. 13 shows a spin valve sensor 300 which is the same as the spinvalve sensor 200 in FIG. 12 except a spin filter layer (SF) 302 islocated between the second free film 222 and the cap layer 224. Upontesting the spin valve sensor 300 it was found that the negativeferromagnetic coupling field −H_(F) was −8 Oe as shown by Example 2 inFIG. 17. It can be seen that the negative magnetic coupling field ofExample 2 had dropped by 50% as compared to the negative ferromagneticcoupling field −H_(F) for Example 1 in FIG. 12. The thickness andmaterial of the spin filter layer 302 was 10 Å of copper (Cu). While anegative ferromagnetic coupling field −H_(FC) of −8 Oe may be desirablefor biasing the free layer 216, it is too low to provide any offset whenthe thickness of the spacer layer 214 is decreased for the purpose offurther increasing the dr/R.

EXAMPLE 3

The spin valve sensor 400 in FIG. 14 is the same as the spin valvesensor 300 in FIG. 13 except a top portion 402 of the second free film222 has been oxidized. Accordingly, the second free film has anunoxidized portion 222 of nickel iron (NiFe) and an oxidized portion 402which is composed of nickel iron oxide (NiFeO). The oxidized filmportion 402 is located directly between the unoxidized film portion 222and the spin filter layer 302. After sputter depositing the second freefilm 222 oxygen was exposed into the sputtering chamber and the secondfilm was exposed to the oxygen for 30 seconds at approximately 2×10⁻⁵Torr. This exposure caused the oxidized portion 402 to develop. The spinvalve sensor 400 was tested for its negative ferromagnetic couplingfield −H_(FC) and it was found to be −16 Oe which is shown at Example 3in FIG. 17. Accordingly, the present invention, shown in FIG. 14,completely restored the negative ferromagnetic coupling field to a valueobtained in Example 1 so that the spin filter layer 302 can be employedfor obtaining the advantages of the spin filter layer as explainedhereinbelow. It is speculated that the increase in the negativeferromagnetic coupling is due to the fact that the oxidization caused asmoother interface between the layers 222 and 302.

The thickness of the copper layer 302 in FIG. 14 was then varied inorder to determine the effect of this thickness on resistance R of thespin valve sensor, the effect on the change in resistance dr of the spinvalve sensor, the change on the magnetoresistive coefficient dr/R of thespin valve sensor, the change in uniaxial anisotropy field H_(K) of thespin valve sensor and the change in easy axis coercivity H_(C) of thespin valve sensor, as shown in FIGS. 17-20, respectively. The thicknessof the spin filter layer 302 was tested without the spin filter layerand then with thicknesses of the spin filter layer of 5 Å, 10 Å, 15 Åand 20 Å. Without the spin filter it can be seen from FIG. 17 that theresistance R was 24, that from FIG. 18 the change in resistance dr was1.8, from FIG. 19 that the magnetoresistive coefficient dr/R was 8, fromFIG. 20 that the uniaxial anisotropy field H_(K) was 12.5 and from FIG.21 that the easy axis coercivity H_(C) was 7. When the spin filter layerwas 5 Å thick the resistance R was 23, the change in resistance dr was1.9, the magnetoresistive coefficient dr/R was 8.3, the uniaxialanisotropy field H_(K) was 10 Oe and the coercivity H_(C) was 6.7 Oe, asshown in FIGS. 17-20, respectively. When the thickness of the spinfilter layer was increased to 10 Å the resistance R was 22, the changein resistance dr was 1.75, the magnetoresistive coefficient dr/R was8.15, the uniaxial anisotropy field H_(K) was 9 Oe and the coercivityH_(C) was 6.2 Oe, as shown in FIGS. 17-20, respectively. When thethickness of the spin filter layer was increased to 15 Å the resistanceR was 20.5, the change in resistance dr was 1.6, the magnetoresistivecoefficient dr/R was 7.95, the uniaxial anisotropy field H_(K) was 9.5Oe and the coercivity H_(C) was 15 Oe, as shown in FIGS. 17-20,respectively. When the thickness of the spin filter layer was furtherincreased to 20 Å the resistance R was 19, the change in resistance drwas 1.45, the magnetoresistive coefficient dr/R was 7.65, the uniaxialanisotropy field H_(K) was 10 Oe and the coercivity H_(C) was 6.4 Oe, asshown in FIGS. 17-20. It is desirable that the thickness of the spinfilter layer be optimized for maximizing the magnetoresistivecoefficient dr/R as shown in FIG. 19. Accordingly, optimum thickness forthe spin filter layer is approximately 6 Å which will achieve amagnetoresistive coefficient dr/R of 8.45. It can also be seen from FIG.20 that when the thickness of the spin filter layer is 6 Å that theuniaxial anisotropy field H_(K) is at a minimum at 7.5 Oe. This isdesirable so that the free layer has soft magnetic characteristics forresponding freely to field signals from the rotating magnetic disk.Further, the coercivity H_(C) in FIG. 21 is nearer its low point whenthe thickness of the spin filter layer is about 6 Å. This furtherindicates that the free layer has soft magnetic properties which aredesirable. A desirable range for the thickness of the spin filter layerwould be between 5-7 Å, as shown from FIG. 19. When the thickness of thespin filter layer was 6 Å the resistance R was 22, the change inresistance dr was 1.85, the magnetoresistive coefficient dr/R was 8.45,the uniaxial anisotropy field H_(K) was 7.5 Oe and the coercivity H_(C)was 6.3 Oe, as shown in FIGS. 17-20, respectively.

EXAMPLE 4

The spin valve sensor 500 in FIG. 15 is the same as the spin valvesensor 400 in FIG. 14 except a top portion 502 of the spin filter layer302 has been oxidized. Accordingly, the spin filter layer has anunoxidized film portion of copper (Cu) and an oxidized film portion ofcopper oxide (CuO) 502. The oxidized film portion 502 is located betweenthe unoxidized film portion 302 and the cap layer 224. Upon testing thespin valve sensor 500 it was found that the negative ferromagneticcoupling field −H_(F) was −15 Oe as shown in Example 4 in FIG. 17.Accordingly, the negative ferromagnetic coupling field of Example 4 issubstantially the same as the negative ferromagnetic coupling field ofExample 3.

EXAMPLE 5

The spin valve sensor 550 in FIG. 16 is the same as the spin valvesensor 500 in FIG. 15 except the spin filter layer 552 in FIG. 16 isonly 6 Å thick and is shown oxidized throughout its thickness. As statedin Example 3 this thickness is the optimized and preferred thickness forthe spin filter layer. This is shown by FIGS. 17-23.

EXAMPLE 6

The spin valve sensor 600 in FIG. 23 is the same as the spin valvesensor 550 in FIG. 13 except a free layer 602 is provided which has athird free film (F3) 604 which was deposited as 15 Å of cobalt iron(CoFe). The third free film 604 has an unoxidized film portion of cobaltiron 604 and an oxidized film portion 606 which is cobalt iron oxide(CoFeO).

EXAMPLE 7

The spin valve sensor 700 in FIG. 24 is the same as the spin valvesensor 600 in FIG. 23 except each of the first and second free films 220and 222 have an unoxidized portion and an oxidized portion. The firstfree film 220 has an unoxidized film portion of cobalt iron (CoFe) andan oxidized film portion 702 of cobalt iron oxide (CoFeO). The secondfilm 222 has an unoxidized film portion 222 and an oxidized film portion704 of cobalt iron oxide (CoFeO).

EXAMPLE 8

The spin valve sensor 800 in FIG. 25 is the same as the spin valvesensor 700 in FIG. 24 except the spin filter layer 552 of FIG. 16 isemployed.

DISCUSSION

All of the oxide films may be formed in the same manner as the oxidefilm 402 in FIG. 14. It should be understood that the forming of thevarious layers may be accomplished in any type of sputtering system,such as RF or DC sputtering, ion beam sputtering or magnetronsputtering. It should be understood that the tantalum (Ta) 224 in allembodiments may be fully or partially oxidized.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

1. A method of making a magnetic read head which has an air bearingsurface (ABS), comprising the steps of: making a spin valve sensorincluding the steps of: forming a ferromagnetic pinned layer that has amagnetic moment; forming a pinning layer exchange coupled to the pinnedlayer for pinning the magnetic moment of the pinned layer; forming afree layer; forming a nonmagnetic conductive spacer layer between thefree layer and the pinned layer; forming a capping layer with the freelayer being located between the spacer layer and the capping layer;forming the free layer with an oxidized film portion and an unoxidizedfilm portion with the oxidized film portion being located between theunoxidized film portion and the capping layer; forming a copper layerbetween the oxidized film portion of the free layer and the cappinglayer; forming nonmagnetic nonconductive first and second read gaplayers; forming the spin valve sensor between the first and second readgap layers; forming ferromagnetic first and second shield layers; andforming the first and second read gap layers between the first andsecond shield layers, wherein the unoxidixed film portion of the freelayer is formed as a nickel iron film and the oxidized film portion ofthe free layer is formed as a nickel iron oxide film.
 2. The method asclaimed in claim 1 further including forming the copper layer fullyoxidized or with an oxidized film portion and an unoxidized filmportion.
 3. The method as claimed in claim 1 wherein the pinning layeris formed of platinum manganese.
 4. The method as claimed in claim 3wherein the making of the spin valve sensor further includes the stepsof: forming first and second seed layers with the first seed layercomposed of nickel manganese oxide and the second seed layer composed oftantalum with the second seed layer being located between the first seedlayer and the pinning layer; and forming the first read gap layer ofaluminum oxide.
 5. The method as claimed in claim 4 wherein the copperlayer is formed 4-10 Å thick.
 6. The method as claimed in claim 5wherein the capping layer is formed of tantalum.
 7. The method asclaimed in claim 6 wherein a forming of the pinned layer comprises thesteps of: forming ferromagnetic first and second antiparallel (AP)pinned films with the first AP film interfacing the pinning layer; andforming an antiparallel (AP) coupling film between the first and secondAP films.
 8. A method of making a magnetic read head which has an airbearing surface ABS, comprising the steps of: making a spin valve sensorincluding the steps of: forming a ferromagnetic pinned layer that has amagnetic moment; forming a pinning layer exchange coupled to the pinnedlayer for pinning the magnetic moment of the pinned layer; forming afree layer; forming a nonmagnetic conductive spacer layer between thefree layer and the pinned layer; forming a capping layer with the freelayer being located between the spacer layer and the capping layer;forming the free layer with an oxidized film portion and an unoxidizedfilm portion with the oxidized film portion being located between theunoxidized film portion and the capping layer; and forming a copperlayer between the oxidized film portion of the free layer and thecapping layer; forming nonmagnetic nonconductive first and second readgap layers; forming the spin valve sensor between the first and secondread gap layers; forming ferromagnetic first and second shield layers;and forming the first and second read gap layers between the first andsecond shield layers, wherein the unoxidized film portion of the freelayer is formed as a cobalt iron film and the oxidized film portion ofthe free layer is formed as a cobalt iron oxide film, and wherein thefree layer is further formed with a nickel iron film with the cobaltiron film being located between the spacer layer and the nickel ironfilm.
 9. The method as claimed in claim 8 wherein the free layer furtherincludes forming a nickel iron oxide film between the nickel iron filmand the cobalt iron film.
 10. A method of making magnetic head assemblythat has an air bearing surface (ABS), comprising the steps of: making awrite head including the steps of: forming ferromagnetic first andsecond pole piece layers in pole tip, yoke and back and regions whereinthe yoke region is located between the pole tip and back gapregionforming a nonmagnetic nonconductive write gap layer between thefirst and second pole piece layers in the pole tip region; forming aninsulation stack with at least one coil layer embedded therein betweenthe first and second pole piece layers in the yoke region; andconnecting the first and pole piece layers at said back gap region; andmaking a read head including the steps of: forming nonmagneticnonconductive first and second read gap layers: forming a spin valvesensor between the first and second read gap layers; forming the firstand second read gap layers between the first shield layer and the firstpole piece layer; and a making of the spin valve sensor comprising thesteps of: forming a ferromagnetic pinned layer that has a magneticmoment; forming a pinning layer exchange coupled to the pinned layer forpinning the magnetic moment of the pinned layer; forming a free layer;forming a nonmagnetic conductive spacer layer between the free layer andthe pinned layer; forming a capping layer with the free layer beinglocated between the spacer layer and the capping layer; forming the freelayer with an oxidized film portion and an unoxidized film portion withthe oxidized film portion being located between the unoxidized filmportion and the capping layer; and forming a copper layer between theoxidized film portion of the free layer and the capping layer, whereinthe unoxidized film portion of the free layer is formed as a nickel ironfilm and the oxidized film portion of the free layer is formed as anickel iron oxide film.
 11. The method as claimed in claim 10 furtherincluding forming the copper layer fully oxidized or with an oxidizedfilm portion and an unoxidized film portion.
 12. The method as claimedin claim 10 wherein the pinning layer is formed of platinum manganese.13. The method as claimed in claim 12 wherein the making of the spinvalve sensor further includes the steps of: forming first and secondseed layers with the first seed layer composed of nickel manganese oxideand the second seed layer composed of tantalum with the second seedlayer being located between the first seed layer and the pinning layer;and forming the first read gap layer of aluminum oxide.
 14. The methodas claimed in claim 13 wherein the copper layer is formed 4-10 A thick.15. The method as claimed in claim 14 wherein the capping layer isformed of tantalum.
 16. The method as claimed in claim 15 wherein aforming of the pinned layer comprises the steps of: formingferromagnetic first and second antiparallel (AP) pinned films with thefirst Ap film interfacing the pinned layer; and forming an antiparallel(AP) coupling film between the first and second AP films.